Preparation and development of equine hyperimmune globulin F(ab′)(2) against severe acute respiratory syndrome coronavirus

Aim: The resurgence of severe acute respiratory syndrome (SARS) is still a threat because the causative agent remaining in animal reservoirs is not fully understood, and sporadic cases continue to be reported. Developing high titers of anti‐SARS hyperimmune globulin to provide an alternative pathway for emergent future prevention and treatment of SARS. Methods: SARS coronavirus (CoV)F69 (AY313906) and Z2‐Y3 (AY394989) were isolated and identified from 2 different Cantonese onset SARS patients. Immunogen was prepared from SARS‐CoV F69 strain. Six health horses were immunized 4 times and serum was collected periodically to measure the profile of specific IgG and neutralizing antibodies using indirect enzyme‐linked immunosorbent assay and a microneutralization test. Sera were collected in large amounts at the peak, where IgG was precipitated using ammonium sulphate and subsequently digested with pepsin. The product was then purified using anion‐exchange chromatography to obtain F(ab′)(2) fragments. Results: The specific IgG and neutralizing antibody titers peaked at approximately week 7 after the first immunization, with a maximum value of 1:14210. The sera collected at the peak were then purified. Fragment of approximately 15 g F(ab′)(2) was obtained from 1 litre antiserum and the purity was above 90% with the titer of 1:5120, which could neutralize the other strain (SARS‐CoV Z2‐Y3) as well. Conclusion: This research provides a viable strategy for the prevention and treatment of SARS coronavirus infection with equine hyperimmune globulin, with the purpose of combating any resurgence of SARS.